(a) Field of the Invention
The present invention relates to a setting mechanism with detent steps for tripping devices of electrical switchgear. More particularly, it relates to low-voltage circuit breakers having an insulating material housing and a setting member accessible on the outside of the switching device and having an inner portion which includes a bearing part for rotatably supporting the setting member.
(b) Discussion of the Prior Art
Setting mechanisms of this type have been described, for instance, in British Pat. No. 1,400,039 and U.S. Pat. No. 3,831,120. There, the purpose of setting the thermal or magnetic tripping devices of switches to release at a given current level is accomplished by turning an outer setting member. The force applied is transmitted to an inner element which moves parts belonging to the tripping devices, such as magnet armatures, setting members for bimetallic strips or the like, where, in general, restoring forces must be overcome. Once selected, the setting should not change by itself under the forces experienced in ordinary operation. A detent system is provided as part of the setting device which must, therefore, be capable of withstanding the restoring forces of the internal parts of the tripping devices as well as external, operation-related forces. To meet these requirements, present setting mechanisms provide components corresponding in number to the steps required. In this connection, the setting mechanism of German Auslegeschrift 10 67 514 provides a further example. There, an outer part of a setting element is mounted on a round shaft which, in turn, is held in bearing parts. The inner portion of the setting member consists of an eccentric which is mounted on an eccentric shoulder of the outer setting meber. A lever fastened on the round shaft is provided for detenting the outer setting or driving member, being forced by a spring against the bearing part of the housing. The lever has a detent edge which engages detent slots on the inside of the outer setting member.
Ring snap-in connections for the assembly of parts are known in the art, being used for connecting machine parts and in precision mechanics. (Journal "Konstruktion", 29, 1977, No. 10, pp. 387-397; Journal "Verbindunstechnik", No. 7/8, 1977, pp. 29-33.)
It is an object of the invention to reduce the number of parts required for the manufacture of setting devices of the type described, and, at the same time, the space required.